Lithium ion secondary batteries, which have characteristics such as compact size, light weight, high energy-density, and rechargeability, are used in a wide variety of applications. Therefore, to increase the performance of lithium ion secondary batteries even further, improvements in battery members such as electrodes have been considered in recent years.
A positive electrode for a lithium ion secondary battery generally includes a current collector and an electrode mixed material layer (positive electrode mixed material layer) formed on the current collector. This positive electrode mixed material layer is, for example, formed by applying a slurry composition onto the current collector and drying the slurry composition. The slurry composition is, for example, formed by dispersing a positive electrode active material, conductive material, binder, and the like in a dispersion medium.
Conventionally, polyvinylidene fluoride (PVDF), a copolymer containing an acid functionality-containing monomer unit, or the like has been used as the binder blended into the slurry composition used to form the positive electrode mixed material layer (for example, see JP 4438104 B2 (PTL 1) and JP 4904709 B2 (PTL 2)). An organic dispersion medium such as N-methylpyrrolidone is used as the dispersion medium that is used to prepare the slurry composition.